I noticed that increasing the area only support left and right. However, I use multi-monitors as top and bottom not left and right, so I would like to have the ability to increase the top and bottom area as well for easier snapping.
Aren't the snap areas already fully configurable? I disabled the default areas and remapped all my screens the way I wanted.
You can customize the appearance of the area, the size (in all directions), the position, and the effect (BTT supports also vertical 1/3 and 2/3 in addition to the default options, plus you can set custom sizes based on what you need).
In the "Standard settings" I went to "Window snapping & moving" and unchecked "enable window snapping". Then I went to BTT's keyboard shortcuts and created an easy to remember shortcut for all the available window sizes and for the actions that move the active window to another monitor since I use a 2nd screen pretty often. At this point I opened the finder and used the keyboard shortcuts to resize the window, click on BTT icon, go to snap areas (advanced feature), create new snap area (use active window as template). At this point you can fully customize the snap area and move it freely around the screen. Go through all the areas that you want to configure, use custom sizes if you need them.
You can also have multiple snap areas in different points of your monitor performing the same action. This way you drag the window to the closest area that does what you want. You can also trigger snap areas using gestures or configure sequences that open, move and resize multiple windows.